Methods of fabricating capacitor

ABSTRACT

A fabricating method of a capacitor is disclosed. Particularly, a fabricating method of a capacitor which forms a capacitor in the place where the insulation layer of an STI region is removed, preventing interlayer dielectric layers from becoming thick. A disclosed method comprises: defining an STI region in the predetermined region of a substrate; removing the insulation layer of the STI region where a capacitor will be formed; forming a gate insulation layer and a first polysilicon layer on the substrate, and patterning the first polysilicon layer; and forming a first insulation layer and a second polysilicon layer on the substrate, and patterning the first insulation layer and the second polysilicon layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a capacitor and a method of fabricatingthe same, and more particularly, to a capacitor in a shallow trenchisolation (hereinafter referred to as “STI”) region, and a method offabricating the same. The present invention may increase the capacitanceper unit area of the capacitor, and/or may reduce an interlayerdielectric layers thickness.

2. Background of the Related Art

Referring to FIG. 1 a, a field oxide layer 11 and a gate oxide layer 12are formed for the insulation between devices on a semiconductorsubstrate 10. A first polysilicon layer 13, which may be used as a gateelectrode and a lower electrode of a capacitor, is deposited on the gateoxide layer 12 and doped.

Referring to FIG. 1 b, using a selective dry etch process and a mask, agate electrode 14 is formed on the gate oxide layer 12 and a lowerelectrode 15 of a poly-insulator-poly (hereinafter referred to as “PIP”)capacitor is formed on the field oxide layer 11.

Referring to FIG. 1 c, an insulation layer 16 is blanket deposited onthe substrate, including where the gate electrode 14 and the polysiliconlower electrode 15 are formed. The insulation layer 16 may be formed bydepositing an oxide layer (e.g., SiO₂) using a LPCVD (low pressurechemical vapor deposition) process.

Referring to FIG. 1 d, a second polysilicon layer 17 for an upperelectrode of a PIP capacitor is deposited on the insulation layer 16.

Referring to FIG. 1 e, the upper electrode 18 of a PIP capacitor isformed using a selective dry etch process and a mask. During a secondstage of the etch process, the insulation layer 16 (except under theupper electrode 18) is removed.

Referring to FIG. 1 f, a source and a drain of a MOS transistor areformed using an ion implantation process, and an insulation layer 20(e.g., comprising TEOS (tetra-ethyl-ortho-silicate) layer and/or a BPSG(borophosphosilicate glass) is formed through a CVD (chemical vapordeposition) process. Contact holes are formed to connect overlying metalinterconnects with the source, the drain, and the lower electrode of thePIP capacitor. Contact plugs 19 are then formed by filling metals intothe contact holes.

Korean Patent Publication No. 2003-0072111 describes a method offabricating a PIP capacitor on a field oxide layer. More particularly,the method reduces resistance-capacitance (hereinafter referred to as“RC”) delay and gate sheet resistance by implanting POCl₃ ions or P ionsinto the polysilicon layer of a gate electrode and a capacitor. KoreanPatent Publication No. 2002-0030420 describes a method which enhancesthe linear characteristic of a capacitor by forming the lower electrodeof a capacitor with a silicon layer and a silicide layer, and formingthe upper electrode of the capacitor with a metal. U.S. Pat. No.6,492,224 describes a method of fabricating the lower electrode of acapacitor by etching the insulation layer of an STI region, then fillingthe etched trench with polysilicon.

However, in the prior method(s) of fabricating both a PIP capacitor anda MOS transistor, the PIP capacitor is formed on the field oxide layeror on the STI layer, and both a gate electrode and at least onepolysilicon layer of a capacitor are formed using the same polysiliconlayer. Consequently, when the lower electrode of the capacitor and thegate are formed from the same polysilicon layer, a height profiledifference between the gate electrode and the capacitor arises, plasmadamage may be caused, and the interlayer dielectric may thicken, makingcontact plug formation more difficult.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a capacitor and amethod of fabricating the same that substantially obviates one or moreproblems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a capacitor and methodof fabricating the same which prevents interlayer dielectric layers fromthickening and embodies a capacitor with high capacitance. These objectsmay be achieved by fabricating a capacitor in a STI trench.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, afabricating method of a capacitor comprises: defining an STI region in asubstrate; removing an insulation layer of the STI region where acapacitor will be formed; forming a gate insulation layer and a firstpolysilicon layer on the substrate, and patterning the first polysiliconlayer; and forming a first insulation layer and a second polysiliconlayer on the substrate, and patterning the first insulation layer andthe second polysilicon layer.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 a through FIG. 1 f are cross-sectional views illustrating aconventional example of fabricating a PIP capacitor and a gateelectrode.

FIG. 2 a through FIG. 2 e are cross-sectional views illustrating anexample of the present process of fabricating a capacitor in accordancewith an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

Referring to FIG. 2 a, an STI region 22 is defined for device isolationin a predetermined region of a semiconductor substrate 21. Next, aconductive well 30 is formed in the semiconductor substrate 21 and anion implantation process is performed to adjust the threshold voltage ofa device (not shown). In the STI region for forming a capacitor,conductive well 30 may form a lower electrode of the capacitor. Becausea capacitor will be formed in the STI region 22, the STI region 22should have space enough for the capacitor.

Referring to FIG. 2 b, after the substrate in which the STI region isformed is coated with a photoresist 23, the photoresist is patternedusing a reticle and an exposure and development process to expose theSTI region for a capacitor. The insulation layer of the STI region for acapacitor and the photoresist pattern are then removed respectively by awet etch.

Referring to FIG. 2 c, a gate insulation layer 24 is formed on thesubstrate, except for the regions where the insulation layer of the STIstill remains. A first polysilicon layer is blanket-deposited on thegate insulation layer 24, and then a patterning process is carried outto form an intermediate capacitor electrode 25. Preferably, the gateinsulation layer 24 is grown by a thermal oxidation process.

Referring to FIG. 2 d, a first insulation layer 26 as a capacitordielectric is deposited on the first polysilicon layer 25, and a secondpolysilicon layer 27 is deposited on the first insulation layer 26. Thesecond polysilicon layer and the first insulation layer are thenpatterned, preferably such that an area of first polysilicon layer 25sufficient to form a via thereto is uncovered by second polysiliconlayer 27 and first insulation layer 26. The first insulation layer 26functions as the dielectric layer of a PIP capacitor, and preferably hasan oxide-nitride-oxide (hereinafter referred to as “ONO”) structure.However, if necessary, the first insulation layer may comprise atransition element oxide, rare earth element oxide or a ferroelectricsuch as BaTiO₃, PbTiO₃ and SrTiO₃. Here, a transistor gate 27 a issimultaneously patterned with the second polysilicon layer 27.

If the second polysilicon layer is deposited after the first polysiliconlayer has been patterned to the height of the substrate, not only theupper capacitor electrode and the gate electrode may be simultaneouslyformed, but also misformation of contacts may be reduced in a subsequentcontact plug forming process. Furthermore, when the capacitor electrodesare formed from the first and second polysilicon layers in a STI trenchregion, the degree of semiconductor device integration and/orcapacitance, which depends on the contact area between electrodes, andspace for forming contact plugs to such electrodes are preferablyconsidered.

Referring to FIG. 2 e, after an interlayer dielectric layer 28 isdeposited over the substrate (including where the capacitor has beencompleted), contact holes are formed by patterning the interlayerdielectric layer. Next, a metal layer is deposited on the substrate andis planarized to form the contact plugs 29. The patterning process ofthe interlayer dielectric layer is carried out by considering both thecontact plugs for the capacitor electrodes and the contact plugs for thetransistor.

Accordingly, the disclosed methods prevent interlayer dielectric layersfrom unnecessarily thickening by fabricating a capacitor in the placewhere the insulation layer of an STI region has been removed. Inaddition, capacitance may be twice as large as that of a conventionaltwo-electrode capacitor. This is because two capacitors, one capacitorcomprising the first polysilicon layer and the second polysilicon layerand another capacitor comprising the first polysilicon layer and theconductive well in the lower part of the substrate, are simultaneouslymade.

It is noted that this patent claims priority from Korean PatentApplication Serial Number 10-2003-0101063, which was field on Dec. 31,2003, and is hereby incorporated by reference in its entirety.

The foregoing embodiments are merely exemplary and are not to beconstrued as limiting the present invention. The present teachings canbe readily applied to other types of apparatuses. The description of thepresent invention is intended to be illustrative, and not to limit thescope of the claims. Many alternatives, modifications, and variationswill be apparent to those skilled in the art.

1. A capacitor, comprising: a conductive well below an STI region in asubstrate, the conductive well forming a bottom capacitor electrode; afirst capacitor insulation layer in the STI region; an intermediatecapacitor electrode on the first capacitor insulation layer having aside surface not in contact with the first capacitor insulation layer; asecond capacitor insulation layer on the intermediate capacitorelectrode; an upper capacitor electrode on the second capacitorinsulation layer; and a third insulator layer having first, second andthird vias respectively communicating with the conductive well and theintermediate and upper capacitor electrodes, wherein the first viadirectly communicates with the conductive well.
 2. A capacitor asdefined by claim 1, wherein the second capacitor insulation layercomprises a member selected from the group consisting of anoxide-nitride-oxide (ONO) layer, a transition element oxide, a rareearth element oxide, and a ferroelectric.
 3. A capacitor as defined byclaim 2, wherein the intermediate capacitor electrode has an areasmaller than the conductive well, and the upper capacitor electrode hasan area smaller than the intermediate capacitor electrode.
 4. Acapacitor as defined by claim 2, wherein the first capacitor insulationlayer has a uniform thickness.
 5. A capacitor as defined by claim 1,wherein the first capacitor insulation layer is continuous with a gateinsulation layer.
 6. A capacitor as defined by claim 5, wherein thefirst capacitor insulation layer is substantially the same as the gateinsulation layer.
 7. A capacitor as defined by claim 5, furthercomprising a gate electrode on the gate insulation layer.
 8. A capacitoras defined by claim 7, wherein the gate electrode comprises a samematerial as the upper capacitor electrode.
 9. A capacitor as defined byclaim 8, wherein the gate electrode has an upper surface coplanar withthe upper capacitor electrode.
 10. A capacitor, comprising: a conductivewell below an STI region in a substrate, the conductive well forming abottom capacitor electrode; a first capacitor insulation layer in theSTI region; an intermediate capacitor electrode on the first capacitorinsulation layer; a second capacitor insulation layer on theintermediate capacitor electrode, the second capacitor insulation layerhaving an area smaller than the first capacitor electrode; an uppercapacitor electrode on the second capacitor insulation layer; and athird insulator layer having first, second and third vias respectivelycommunicating with the conductive well and the intermediate and uppercapacitor electrodes, wherein the first via directly communicates withthe conductive well.
 11. A capacitor as defined by claim 10, wherein thefirst capacitor insulation layer comprises a member selected from thegroup consisting of an oxide-nitride-oxide (ONO) layer, a transitionelement oxide, a rare earth element oxide, BaTiO₃, PbTiO₃, and SrTiO₃.12. A capacitor as defined by claim 10, wherein the intermediatecapacitor electrode has an area smaller than the conductive well.
 13. Acapacitor as defined by claim 10, wherein the first capacitor insulationlayer has a uniform thickness.
 14. A capacitor as defined by claim 10,wherein the intermediate capacitor electrode has a side surface not incontact with the first capacitor insulation layer.
 15. A capacitor asdefined by claim 10, wherein the first capacitor insulation layer iscontinuous with a gate insulation layer.
 16. A capacitor as defined byclaim 15, wherein the first capacitor insulation layer is substantiallythe same as the gate insulation layer.
 17. A capacitor as defined byclaim 15, further comprising a gate electrode on the gate insulationlayer.
 18. A capacitor as defined by claim 17, wherein the gateelectrode comprises a same material as the upper capacitor electrode.19. A capacitor as defined by claim 18, wherein the gate electrode hasan upper surface coplanar with the upper capacitor electrode.